I think the 3D backgrounds are quite nice ... and you could make one yourself, though I am sure it is not as easy as buying a pre-made deal
I didn't like the plant ones and removed it. I did the black for a while, and got a bit tired of it as well. I also done aluminum foil for a bit and liked it, but later removed it
I like the idea of window tint, darkens the background, still can see through it. Also, if you are certain you want a particular color forever, painting is pretty much maintenance free (just be careful of where power filters rest against it).
A big advantage of a background is hiding the wires/filters.
As of now, I just prefer no background. I never scrape the back (though remarkably free of algae). I figure, let the Oscar see out of the back, it most likely gives it the appearance of more space and room. I know if I was trapped in a box, I would like to see out as many directions as possible ;